Underlying problem?? : replaced both front O2 sensors and both cat converters.

What is your question?

In less than 3 months I have had a service engine light with codes for both front O2 sensors and both cat converters. The O2 sensors went out first, one at a time, then the front cat converter, now the rear cat converter. I only run premium BP fuel. I think there must be a underlying problem. I am also beginning to smell a oh so slight burning odor and slight ticking at idle. It all been under warranty as the vehicle on has 28K miles. The car is garage kept and taken care of. Ideas to take to the dealership would be appreciated.